This invention relates to mining machines and, in particular, continuous coal mining machines which are equipped with a device which can be used for installing roof support bolts as the mining machine advances along a mine entry.
Much underground coal mining is done by continuous mining machines which remove coal along the full height of the coal seam and include a gathering and conveying system so that the machine can advance while it mines. In order for such machines to advance greater distances into a seam, depending on roof conditions, continuous mining machines have been equipped with devices for installing roof support bolts in the mine roof. This has been done to save time by eliminating the need to back the mining machine out of an entry and have a separate roof bolting machine install the roof bolts.
It has been found that by positioning such a roof bolting unit on each side of a continuous mining machine, two bolts may be installed along the lateral center line of a mine entry. It has also been found that this does not always provide sufficient support for the mine roof and that additional bolts normally must be installed in order to provide safe roof conditions. Thus, even though provision of roof bolting units on a mining machine can provide more efficient installation of roof bolts, additional roof bolts must be installed along the lateral center line of a mine entry which requires use of a separate roof bolting machine and limits the distance a mining machine can advance before the additional bolting operation must be performed.
Whenever these roof bolt installation units are mounted on a continuous mining machine, the bolter operator might be exposed to rocks or debris which might fall from the mine roof while installing the roof bolt. A protective canopy can be provided which operates to shield the operator from falling rock. Such a canopy is normally formed of heavy material and takes up a relatively large amount of space in order to provide adequate protection.